The KRs are the only 2A3s I have that are microphonic at all. It is not a problem, however and the longer I run them the microphonic seems to diminish.
I only have one pair of headphones - LCD3f. With these headphones, I have landed on two tube combos that I find the most musical and enjoyable - U52/KR2A3/Cryo Pearl Reflektor 6N1P OR - U52/Psvane WE275/Box Plate Novosibirsk 6N1P. The KR2A3 combo is, to my ears, more detailed and dynamic but the WE275 tubes are sooo sweet and smooth (the box plate 6N1P adds a little more detail and edge). I can understand why some like a 6BQ7 instead of 6N1P but, again to my ears, the sound gets too wet and tube, especially with the LCD3s.
Also, I have noticed that my cryo pearl Reflektor tube looks identical to my 60's Novosibirsk 6N1Ps. I purchased another Reflector tube and noticed it looked identical to the Voskhod rocket 6N1P (that I don't like so much). So, my conclusion is that Reflektor tubes were made by more than one plant and my preference is the Novosibirsk version.